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Earth Systems ScienceChapter 3
I. Global Energy Balance and the Greenhouse Effect:The Physics of the Radiation Balance of the Earth
1. Electromagnetic Radiation: waves, photons
2. Electromagnetic Spectrum
3. Flux
4. Blackbody Radiation
5. Planetary Energy Balance
ELECTROMAGNETIC RADIATION: WAVES
c = speed of light in a vacuum = 3.0 x 108 m/s = wavelength (m)v = frequency (1/s or s-1)
v = c
= c/v
V/c = 1
ELECTROMAGNETIC RADIATION: WAVES
Relationship between v, c, and
ELECTROMAGNETIC RADIATION: PHOTONS
E = hv = hc/
E = Energy (joules, or j)
h = Planck’s constant = 6.63 x 10-34 j-s
v = frequency (1/s or s-1)
c = speed of light in a vacuum (m/s)
= wavelength (m)
ELECTROMAGNETIC SPECTRUM
http://www.lbl.gov/MicroWorlds/ALSTool/EMSpec/EMSpec2.html
FLUX
FLUX: INVERSE SQUARE LAW
BLACKBODY RADIATION
Planck function Wien’s Law Stefan-Boltzman law
BLACKBODY RADIATION
T = temperature (K)
= Stefan – Boltzman constant
BLACKBODY EMISSION RATES:PLANCK FUNCTIONS FOR SUN,EARTH
At the Sun’s surface
RADIATION BALANCE OF THE EARTH:
SOLAR (SHORTWAVE) RADIATION
Note: area of circle is used here: r2
SWin = area * fluxSWin = r2S - r2SASWin = r2S(1-A)
RADIATION BALANCE OF THE EARTH:
SOLAR (SHORTWAVE) RADIATION:
Why we use the area of a circle
Earth
RADIATION BALANCE OF THE EARTH:
SOLAR (SHORTWAVE) RADIATION:
Why we use the area of a circle
Earth
RADIATION BALANCE OF THE EARTH:
SOLAR (SHORTWAVE) RADIATION
Net SW = Incoming – Outgoing
Net SW = r2S – r2SA
Net SW = r2S (1-A)
Earth’sEnergy
SWin SWout
RADIATION BALANCE OF THE EARTH:
TERRESTRIAL (LONGWAVE) RADIATION
Earth
Note: area of sphere is used here: 4r2
LWout = area * fluxLWout = 4r2Te
4
RADIATION BALANCE OF THE EARTH:
TERRESTRIAL (LONGWAVE) RADIATION
Net LW = Incoming – Outgoing
Net LW = 0 – 4r2Te4
Net LW = -4r2Te4
Earth’sEnergy
LWout
Net LW = -4r2Te4
Te = effective radiating temperature
Earth’sEnergy
LWout
RADIATION BALANCE OF THE EARTH:
TERRESTRIAL (LONGWAVE) RADIATION
RADIATION BALANCE OF THE EARTH: TOTAL RADIATION
Assume dynamic equilibrium: IN = OUTNet SW + Net LW = 0Net SW = r2S(1-A)Net LW = -4r2Te
4
r2S(1-A) – 4r2Te4 = 0
Te4 = (S/4) (1-A)
Te = [ (S/4) (1-A) ]0.25
Earth’sEnergy
SWinSWout
LWout
RADIATION BALANCE OF THE EARTH: TOTAL RADIATION
Te = [ (S/4) (1-A) ]0.25
S = 1370 W/m2
A = 0.3 = 5.67 x 10-8 W/(m2-K4)
Te = 255K = -18°C = 0°F
RADIATION BALANCE OF THE EARTH:GREENHOUSE EFFECT
Te = 255K
Ts = 288K
Tg = Ts-Te
Tg = 33K = 33°C = 59°F
RADIATION BALANCE OF THE EARTH:GREENHOUSE EFFECT
Earth’s Surface
Earth’s Atmosphere
SW LW You can do the same calculation including an atmosphere
Atmospheric Energy Balance
II. Atmospheric Composition and Structure
Vertical Pressure and Temperature Structure
Note: logarithmic scale !
Vertical Ozone Structure
Modes of Energy Transfer in the Atmosphere
Physical Causes of the Greenhouse Effect
Physical Causes of the Greenhouse Effect
Physical Causes of the Greenhouse Effect
Effects of Clouds on the Atmospheric Radiation Budget: SW radiation
SW A*SW SW A*SW
Effects of Clouds on the Atmospheric Radiation Budget: LW radiation
Globally Average Energy Budget
Introduction to Climate Modeling
Many types of climate models exist. We discuss some of the more common types, which have different levels of complexity:
• Zero-dimensional radiation balance models
• 1-dimensional radiative-convective models
• 2-dimensional diffusive models
• 3-dimensional Atmospheric General Circulation Models (AGCM)
• 3-D coupled atmosphere – ocean models (AOGCM)
Te = [ (S/4) (1-A) ]0.25
Earth’sEnergy
SWinSWout
LWout
Introduction to Climate Modeling:zero-dimensional radiation balance model
Introduction to Climate Modeling:1-dimensional radiative-convective model
One-Layer Radiation Model
Introduction to Climate Modeling:1-dimensional radiative-convective model
1-D Rad-Conv Model
surface
S/4 (S/4)*A
Radiation in each wavelength band
Convection, latent fluxes
Surface: latent, sensible
Introduction to Climate Modeling:2-dimensional climate model
Surface
North Pole
South Pole
http://www.arm.gov/docs/documents/project/er_0441/bkground_5/figure2.html
Introduction to Climate Modeling:3-dimensional General Circulation Model (GCM)
surface
Introduction to Climate Modeling:3-D coupled atmosphere – ocean models
Atmosphere
Ocean
Climate Feedbacks
Water vapor feedback
snow/ice albedo feedback
IR flux/temp feedback
Cloud feedback ???